Air conditioning system

ABSTRACT

A self-contained, fully-integrated, energy efficient heating and cooling system or apparatus for conditioning the air on the interior of a building which includes a means for creating airflow through the apparatus, a section for cooling the airflow, a section for heating the airflow, a means for directing the airflow into the cooling section or into the heating section, a reheat device for tempering (i.e., reheating) the airflow exiting the cooling section, a return air section for receiving air returned to the apparatus from the building interior, and a means for pulling the returned air out of the return air section and venting the returned air to the environment outside of the building. The heating section of the present invention also provides a “four-pass” heat exchanger which may be assembled from sections of cast iron or other suitable materials, and a high efficiency combustion burner which may be integrated into the four-pass heat exchanger.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/340,621 filed on Dec. 13, 2001 entitled “Heat Exchanger and Burner”the disclosure of which is incorporated as if fully rewritten herein.

TECHNICAL FIELD

This invention relates generally to heating and cooling systems for usein commercial buildings, and specifically to the components included insuch heating and cooling systems, particularly cooling devices, heatingdevices, and heat exchanger assemblies.

BACKGROUND OF THE INVENTION

Air conditioning or air handling units that include both heating andcooling capabilities are commonplace in modern society. Powerfulindustrial or commercial air conditioning systems are often utilized tocondition (i.e., control the temperature and humidity) the air on theinside of buildings such as office towers, warehouses, factories, andschools. Such air conditioners are often very large in size and requiresignificant amounts of space and energy to effectively handle andcondition the air inside such industrial or commercial buildings.

Air conditioning units used for such applications typically includevarious compartments or sections that are dedicated to either heating orcooling the air stream flowing through the unit. In general, the coolingsections of such units include a compressor, an expansion valve, aheated coil, a chilled coil, a heat transfer gas such as Freon, multiplefans, and a control unit. The compressor, which is a pump, compressescool Freon gas, causing it to become hot, high pressure, Freon gas. Thishot gas moves through a set of coils where it dissipates heat andcondenses into a liquid. Heat from this set of coils is dispersed to theoutside environment by a fan which blows air across the heated coils.The liquid then passes through an expansion valve and evaporates tobecome cold, low-pressure Freon gas. The cold gas then runs through asecond set of coils where it absorbs heat from the air inside thebuilding. A second fan disperses the cooled air out of the airconditioner and into the space being cooled.

Prior art air conditioning systems, typically referred to as“multi-zone” or “dual-duct” systems, control the temperature of a roomby varying the temperature of the air delivered to the room. Suchsystems are also referred to as “constant volume” systems because theydeliver a constant airflow to each zone or room in a building. A primaryadvantage of constant volume systems is that they provide the desiredventilation, but do not require an excessive number of system parts anddo not require complicated control sequences. Despite these advantages,constant volume systems are problematic in that they redirect air fromthe cooling section to the heating section of the unit. This redirectionof air results in the final air supply being delivered to the roomwithout the dehumidifying benefit of the system's cooling coil.

Certain other prior art systems that direct 100% of the air handled bythe system through the cooling coil require either (i) an external heatsource to reheat the air before it is delivered to a room or zone; or(ii) a method that reduces the airflow known as “Variable Air Volume(VAV).” VAV systems are typically used in spaces where occupancy of thearea is variable. Thus, there is a need for an air conditioning unitthat utilizes a more efficient means for directing air, and cooled airin particular, through the system.

In many air conditioning units, the condenser coil is located on theoutside of the building that the unit is servicing. The heat generatedby the coil is vented to the outside environment and any energy presentin the form of heat is lost to the environment. Conceivably, this heatedair stream could be directed back into the unit, and the energy from theheated air stream could be captured to increase the efficiency of theunit, i.e., increase output and/or reduce energy consumption. Thus,there is also a need for an increased efficiency air conditioning systemthat is capable of recapturing energy that is typically wasted by priorart systems.

Increased efficiency and/or reduced energy consumption may also beachieved by using certain specialty components within the system or airconditioning unit. One source for increasing efficiency in terms of heatoutput is the system's heat exchanger. Heat exchangers manufactured fromcast iron have been commercially available for many years. Such heatexchangers are typically constructed to include a relatively largecombustion chamber and smaller exhaust passageways which are used toincrease the surface area of the heat exchanger and create greater heatexchange efficiency. The basic purpose of a large combustion chamber orarea is to eliminate impingement of flame directly onto the heatexchanger membrane, thereby increasing the life expectancy of theassembly.

Such heat exchangers are often very large in size and consequently maybe impractical for some applications. Additionally, these heatexchangers cannot typically be adapted to different system requirementsand configurations. Furthermore, if the heat exchanger cracks orfractures, the entire unit must often be replaced. Thus, there is a needfor an increased-efficiency, adaptable, easily serviceable heatexchanger for commercial and residential heating ventilating and coolingsystems.

SUMMARY OF INVENTION

These and other limitations of the prior art are overcome by the presentinvention which provides a self-contained, fully-integrated, energyefficient heating and cooling system or apparatus for conditioning theair on the interior of a building. This heating and cooling systemincludes all of the benefits of the constant volume system whileproviding improved humidity control without the additional energyrequired to reheat cooled air. Unlike commercially available prior artsystems that typically locate the condensing coil on the exterior of abuilding, the present invention locates the condenser coil within thehousing of the unit itself so that conditioned air returned to the unitcan be used to reduced the energy consumption of the condenser coil.Additionally, a secondary heating apparatus, separate and distinct fromthe main heat exchanger, is included with the present invention toprovide tempered air in certain situations. Finally, the presentinvention optionally includes a secondary heat exchanger or energyreclaiming device that further enhances the efficiency and performanceof the unit.

An exemplary embodiment of this invention includes a means for creatingairflow through the apparatus, a section for cooling the airflow, asection for heating the airflow, means for directing the airflow intothe cooling section or into the heating section, a reheat device fortempering (i.e., reheating) the airflow exiting the cooling section, areturn air section for receiving air returned to the apparatus from thebuilding interior, and means for pulling the returned air out of thereturn air section and venting the returned air to the environmentoutside of the building.

The heating section of the present invention also provides a novel“four-pass” heat exchanger a “four-pass” heat exchanger which may bemanufactured from sections of cast iron or other suitable materials, anda high efficiency combustion burner which may be integrated into thefour-pass heat exchanger. Advantages of this invention include improvedefficiency, reduced size, and enhanced performance of the heatexchanger/burner assembly. An automated system for operating dual ductheating and cooling systems which utilize the heat exchanger/burnerassembly of the present invention is also provided.

Further advantages of the present invention will become apparent tothose of ordinary skill in the art upon reading and understanding thefollowing detailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings and figures, which are incorporated in andform a part of the specification, schematically illustrate exemplaryembodiments of the invention and, together with the general descriptiongiven above and detailed description of the exemplary embodiments andexamples given below, serve to explain the principles of the invention.

FIG. 1 is a cross sectional view of an exemplary embodiment of the heatexchanger assembly of the present invention depicting an exemplaryconfiguration of the various sections of the heat exchanger and thepreferred placement of the burner assembly within the heat exchangerassembly.

FIG. 2 a is a side view of an exemplary embodiment of the burnerassembly of the present invention depicting the placement of the burnerassembly in the combustion chamber and showing the placement andorganization gas valve assembly.

FIG. 2 b is a top view of the burner assembly of FIG. 2 a.

FIG. 2 c is a front view of the burner assembly of FIG. 2 a.

FIG. 3 a is a cross-sectional view of an exemplary embodiment of the airconditioning unit of the present invention showing the various sectionsand components of the unit.

FIG. 3 b is a top view of the air conditioning unit of FIG. 3 a.

FIG. 4 a is a cross-sectional view of an alternate embodiment of the airconditioning unit of the present invention wherein an auxiliary heatexchanger or “energy reclaiming device” has been included on theinterior of the unit.

FIG. 4 b is a top view of the air conditioning unit of FIG. 4 a.

FIG. 5 is a diagrammatic representation of the typical flow of airthrough an exemplary embodiment of the air conditioning unit of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a self-contained, fully-integratedheating and cooling system, apparatus, or unit for conditioning the airon the interior of a building or group of buildings. An exemplaryembodiment of this apparatus includes a means for creating airflowthrough the apparatus, a section for cooling the airflow, a section forheating the airflow, a means for directing the airflow into the coolingsection or into the heating section, a reheat device for tempering theairflow exiting the cooling section, a return air section for receivingair returned to the apparatus from the building interior, and a meansfor pulling the returned air out of the return air section and ventingthe returned air to the environment outside of the building.

In the exemplary embodiment, the reheat device is positioned between thecooling section and the heating section, and a portion of the cooled airexiting the cooling section is directed through the reheat device and isreheated by the device before exiting the apparatus to create a streamof tempered air. Preferably, the heating section includes a four-passheat exchanger, although a two-pass heat exchanger may be utilized. Thecooling section includes a refrigeration system that utilizes arefrigerant, a plurality of cooling coils, a condenser coil incommunication with the cooling coils, and a compressor for moving therefrigerant through the cooling coils and the condenser. The coolingcoils and the condenser are all contained within the housing thatsurrounds the various sections and components of the apparatus. Thecomponents of the air conditioning system of the present invention arediscussed in greater detail below.

Heat Exchanger Assembly

As stated above, the air conditioning system of the present inventionprovides both a cooling section and a heating section. Preferably, theheating section includes an increased-efficiency heat exchanger assemblyand an increased-efficiency combustion burner assembly that when usedtogether provide a novel system for transferring heat energy generatedby a combustion source to an air stream for the purpose of heating theair stream, while keeping the heated air stream separate from theproducts of combustion. Preferably, the burner assembly is installed inone of the cylindrical members of the heat exchanger assembly.

An exemplary embodiment of the present invention provides a heatexchanger assembly intended for use in, but not limited to, indirectfired, forced air-heating systems. In general, the heat exchanger of thepresent invention provides a greater than two-pass system wherein theheated gases from a burner make four passes across the surface area ofthe heat exchanger prior to exiting a flue and being vented from thesystem. Prior art heat exchangers typically include only a two pass orthree pass heat exchanger. While the exemplary embodiment of the heatexchanger of the present invention includes four “passes,” those skilledin the art will appreciate that additional passes or gas conduits may beadded to this heat exchanger. For example, six-pass or eight pass heatexchangers are consistent with the design of the present invention. Theexemplary four-pass system of the present invention provides numerousadvantages, as will be apparent to those skilled in the art from thefollowing detailed description.

As best illustrated by FIG. 1, an exemplary embodiment of heat exchangerassembly 10 provides a first cylindrical member 12, first collector box14, first gas conduit 16 and a second gas conduit 18, connectors 20 and22, third gas conduit 24 and fourth gas conduit 26, second collector box28, second cylindrical member 30, section couplers 32, and exhaustconnection 34. Preferably, these components are manufactured fromcommercially available cast iron sections or castings. Typically, thesecommercially available castings include multiple protrusions or finswhich extend outward from the surface of the casting and serve toincrease the surface area of the casting.

As indicated by the arrows in FIG. 1, the products of combustion (i.e.,heated gases) initially flow into first cylindrical member 12 and travelalong the length of first cylindrical member 12 into first collector box14 where the gas stream is divided from a single stream into a doublestream. The divided gas stream flows from first collector box 14 intofirst gas conduit 16 and a second gas conduit 18 which are located oneither side of, and run parallel to, first cylindrical member 12. Aftertraveling the length of gas conduits 16 and 18, the heated gases flowinto connectors 20 and 22. Connectors 20 and 22 direct the gas floweither up, down, left, or right depending on how heat exchanger assembly10 is oriented. The gas flow then enters third gas conduit 24 and fourthgas conduit 26 which are parallel to and adjacent to gas conduits 16 and18. The gas flow travels the length of conduits 24 and 26 and enterssecond collector box 28 where the divided gas stream is re-combined intoa single gas stream. The recombined gas stream then enters and travelsthe length of second cylindrical member 30 were it eventually reachesexhaust connection 34.

Preferably, the various cylindrical members and conduits of heatexchanger assembly 10 are manufactured from individual prefabricatedcastings that, when connected together, form the length of thecylindrical members and conduits. For example, in an exemplaryembodiment, cylindrical member 12 comprises two identical castings thatare bolted together. These castings typically include mating surfacesthat permit assembly using standard machine bolts. Thus, replacement orrepair of the assembly or its components can be accomplished withstandard hand tools. An advantage of this type of construction is thatif one casting cracks or fractures, it can be replaced without replacingthe entire heat exchanger assembly. Thus, the expense of repairing theheat exchanger of the present invention is likely to be significantlyless than repairs for other types of heat exchangers. Furthermore, theoverall length of heat exchanger assembly 10 can be increased ordecreased by simply adding or removing sections (i.e., castings).

In an exemplary embodiment, the placement of gasket material, preferablyhigh temperature glass wool, between the sections of the cylindricalmembers and conduits addresses any possible thermal expansion of theassembly and its components by allowing each section to expand withoutimposing excessive stress on any other section. These gaskets reduce thelikelihood that the sections of heat exchanger will crack or fracturedue to thermal expansion.

The configuration of the cylindrical members and gas conduits shown inFIG. 1 results in the products of combustion, i.e., heated gases,reversing direction at least four times before exiting heat exchangerassembly 10. Consequently, the velocity of the gas passing through thesections is reduced and the time that the heated gas remains in thesections is increased, thereby allowing more efficient transfer of heatfrom the combustion gas though the cast iron into the air stream whichpasses over the heat exchanger.

Preferably, conduits 16, 18, 24, and 26 when viewed in cross section,are “teardrop” shaped. This shape enhances the efficiency of the airflowacross heat exchanger assembly 10 and increases the transfer of heatenergy across the castings to the air stream. This transfer of energyfrom the heated gases to the air stream occurs through the membrane(i.e., the cast iron) of the heat exchanger; however, completeseparation of the combusted gases and this secondary air stream on theexterior of the heat exchanger is maintained. As stated above, a hightemperature gasket material such as glass wool may be placed between thecastings that form conduits 16, 18, 24, and 26 as well as cylindricalmembers 12 and 30 during the construction of heat exchanger assembly 10.This gasket material effectively seals the various sections of the heatexchanger and prevents the heated gases from contaminating the airstream.

The efficiency of heat transfer through the heat exchanger membrane(i.e., cast iron or other metal) is typically a function of contactarea, temperature differential, transmission, convection, and radiance.The preferred configuration of the present invention enhances theconvection aspect of the system's operation, and increases the rate ofenergy transfer. Alternate embodiments of heat exchanger assembly 10include various internal devices that promote turbulent flow of theproducts of combustion thereby further enhancing the efficiency of theexchanger.

Advantageously, the exemplary embodiment of the assembly results in aheat exchanger that is more compact than possible with previously knownconfigurations. The configuration of the preferred embodiment is alsosymmetrical about the vertical and horizontal axis, thereby allowing asingle configuration to be used for up flow, down flow, and horizontalapplications. This configuration also allows the burner to be installedin cylindrical member 12 as shown in FIG. 1, thereby producing a“counter-flow” or to be installed in cylindrical member 30, therebyproducing a “parallel flow” of gases through heat exchanger assembly 10.Counter flow causes the highest temperature combustion gas to occur onthe discharge air of the secondary air stream, thereby furtherincreasing the efficiency of thermal transfer of heat exchanger assembly10.

Heat exchanger assembly 10 can be incorporated into a heating systemwhich utilizes a forced draft burner or an atmospheric draft type burnerwhich combusts multiple fuels. While the preferred embodiment may beutilized with several types of burners, it is particularly suitable foruse with a cylindrical metal fiber burner firing either natural ormanufactured gas such as propane. A novel cylindrical metal fiber burneris described below.

Burner Assembly

The present invention provides a burner assembly designed for use with aheat exchanger that utilizes a cylindrically-shaped combustion chamber.This invention maximizes the efficiency of heat transfer from the burnerassembly to the heat exchanger assembly and increases the overallperformance of the system while reducing harmful emissions such ascarbon monoxide and nitric oxides. Burner assembly 50 may be describedas a parallel positioning system for the attached devices which allowsthe system to compensate for variations caused by differences in thevarious metering devices. Preferably, heat exchanger assembly 10 and theburner assembly 50 operate as an integrated unit. As shown in FIG. 1,first cylindrical member 12 serves as combustion chamber 68 when theburner is inserted into the cylindrical member. Second cylindricalmember 30 may also serve the combustion chamber. In one embodiment, thecylindrical member used as combustion chamber 68 is lined with aninsulating material such as, for example, refractory cement line thatserves to protect the interior surface of the chamber.

As best illustrated by FIGS. 2 a–c, burner assembly 50 includes sparkignition device 52, metal fiber combustion surface 54, flame detectorport 56, flanged mounting adapter 58, fuel/air mixing chamber 60, fuelgas distributor plenum 62, motor operated iris damper 64, screen 66,combustion chamber 68, gas valve subassembly 70, safety gas valve 72,vent valve 74, safety valve 76 and fuel metering valve 78. An exemplaryembodiment of burner assembly 50 also includes flame safety controllersand detectors including UV flame detectors and programmable flame safetycontroller (not shown), as well as gas pressure regulating devices andvolume control devices (not shown).

Spark ignition device 52 includes transformer, ignition wire, and sparkplug 53. Spark ignition device 52 is arranged to furnish an ignitionspark adjacent to the metal fiber combustion surface. Spark ignitiondevice 52 is similar to one manufactured by Westwood ignition products.

Gas valve subassembly 70 includes motorized and solenoid valves. Fuelmetering valve 78 is fitted with the same type of actuator as found in acommercially available Honeywell system. The valve is a Honeywell valveand is specifically designed as part of a burner optimization systemthat independent positioning of each valve to accomplish the optimumcombustion over the entire capacity range of the burner. The applicationof the Honeywell combustion controller allows vent (air) valve 74, fuelvalve 78, and if installed, a flue gas recirculation valve, to operatein response to a preprogrammed positioning sequence.

An exemplary embodiment of burner assembly 50 includes air volumecontrol devices including dampers and actuators. Air inlet valves (e.g.,vent valve 74) precisely control the flow of air into the mixingchamber. An iris type damper (Continental Fan, Buffalo, N.Y.) is asuitable inlet valve. Damper 64 is fitted with a motor actuator toposition the damper to precisely control the airflow into the burner. Acommercially available Honeywell actuator specifically designed to beused with a fuel-air mixture controller is a suitable motor actuator.The motor is designed to control a fuel valve, an air damper, and a fluegas recirculation valve for burners. Combining the use of this motorwith the iris damper is a novel aspect of the burner assembly.

Fuel/air mixing chamber 60 comprises a permeable membrane assembly,which contains the fuel, air mixture and creates a metal fibercombustion surface 54 to enhance the combustion efficiency of the airfuel mixture. The combustion of a gas air mixture within the combustionchamber is precisely controlled by this assembly. Fuel/air mixingchamber 60 promotes complete mixing of the fuel and air prior tocombustion by generating perpendicular flow patterns for the two gasesthat enter the mixing chamber.

Fuel/air mixing chamber 60 includes a cylindrical air inlet 61 with alarger fuel/air mixing chamber 60 surrounding it. Orifice openingsplaced between the chambers direct the fuel gas into the air stream in amanner to create turbulence and increase mixing of the gas and air. Byprecisely metering the air and fuel into the burner, the combustionefficiency can be maximized over the entire capacity range of theburner. The burner of the present invention typically operates at acombustion efficiency of about 85%, which exceeds the current industrystandard of 75 to 80% efficiency. The air fuel mixture is then deliveredto a cylindrical metal fiber combustion surface 54 shaped and sized tomatch the requirements of the system capacity.

The size and location of metal fiber combustion surface 54 is determinedby the requirements of the heat exchanger to which it is applied. Thecombustion surface distributes the flame evenly over the entire face ofthe burner, facilitating the complete mixing and complete combustion ofthe fuel. This enhances the performance of the burner and reducesundesirable and potentially harmful emissions.

An exemplary embodiment of burner assembly 50 includes a draft inducingfan assembly (not shown) to remove the products of combustion from heatexchanger assembly 10. The burner is naturally aspirated and utilizesdraft created by a fan located at the discharge of heat exchangerassembly 10. Fan operation is involved in the operation of burnerassembly 50 and a flow proving interlock is preferably included toassure operation of the draft fan prior to introduction of any fuel intothe burner. Preferably, the draft fan is an integral part of the burner;however, the fan may be located remotely from the heating device.

Preferably, burner assembly 50 also includes an industry standard flamesafety control system (e.g., Honeywell) utilizing an ultra violet flamedetector, program flame safety controller ignition system. Burnerassembly 50 is a fully modulating burner with a high turn down ratio ofabout 20 to 1 with precise control of the air fuel mixture over theentire range of operation. Burner assembly 50 can respond signals forvarious types of control devices as required by the installation forboth start/stop and modulation. Burner assembly 50 can be installed withindustry standard operating and limit controls as required by anygoverning authorities for the installation.

Air Conditioning Unit

The present invention also provides an improved arrangement of systemcomponents for heating, cooling, and dehumidifying buildings, especiallybuildings including multiple zones or rooms which can be served by acentralized air conditioning system. Advantages of the present inventioninclude increased or enhanced energy recovery (i.e., greater energyefficiency) and improved system performance, including improved humiditycontrol.

As shown in FIGS. 3 a and 3 b, and according to an exemplary embodiment,the present invention provides a fully integrated heating and coolingunit 100 enclosed within an encasement or housing. One embodiment ofthis housing provides entrance and egress points (i.e., doors or ports)into and out of the unit which allow easy access to the internalcomponents. The air utilized by unit 100 enters the heating and coolingunit from two primary sources: primary external air intake 200 andreturn air inlet 602. The air drawn into the unit at primary externalair intake 200 is pulled into the unit from the outside environment.This air is commonly referred to as “dilution air” and is necessary forproper ventilation of the building. The second source of air is airreturned to the unit from the conditioned space on the interior of thebuilding. This air is commonly referred to as “return air.”

Unit 100 includes a system of automatically controlled dampers that areconfigured to control the airflow into the units itself and/or into thevarious sections of the unit. In the exemplary embodiment shown in FIG.3 a, first damper 202, fifth damper 606, and seventh damper 614 controlthe flow of air into the unit, either from the external environment orfrom the conditioned space within the building. Likewise, optionalsecond damper 206, third damper 404, fourth damper 416, sixth damper 608are arranged on the interior of the unit to meter the respective amountsof dilution air and return air that are utilized by the system. Thesystem is capable of utilizing of up to 100% of either type of air fordelivery to the conditioned room or zone.

With reference again to FIGS. 3 a and 3 b, upon entering unit 100, airpasses through filters that have variable capacity for the removal ofcontaminants. Air entering the unit at primary external air intake 200(see the arrow labeled “A” in FIG. 5: note that the air flow depicted inFIG. 5 is reversed compared to the air flow entering the unit in FIGS. 3a and 4 a) passes through first filter 204, while air entering the unitat return air inlet 602 passes through third filter 604. From thefilters, both air streams enter blower section 300. Blower 302 providesthe energy required to move the combined air streams through the heatingand cooling sections of the unit, as described below.

Upon passing through first filter 204, air drawn into the unit from theoutside environment flows into blower section 300 (see the arrow labeled“B” in FIG. 5). In an alternate embodiment, the air stream passesthrough second damper 206 and second filter 208, which are optionallyincluded in unit 100. Air returning to unit 100 from the conditionedspace passes through third filter 604 and fifth damper 606 into blowersection 300 (see the arrow labeled “H” in FIG. 5). Blower 302 forces theair through air passage 304 into antechamber 306. From antechamber 306the airflow is directed into cooling section 400 (see the arrow labeled“C” in FIG. 5) or into heating section 500 through fourth damper 416(see the arrow labeled “D” in FIG. 5).

Air that is forced into cooling section 400 passes first over coolingcoils 402 which cool and dehumidify the airflow. The cooled air may thenexit unit 100 at cooled air outlet 408 (see the arrow labeled “E” inFIG. 5). The preferred method of cooling utilizes a compressor drivenrefrigeration cycle using standard refrigerants and including air coilsused both for condensing and evaporation of the refrigerant(s). Thepreferred cooling coil is a direct expansion cooling coil commonlyreferred to a DX cooling coil. In the exemplary embodiment shown in FIG.3 a, compressor 410 is mounted in primary external air intake 200,cooling coils 402 are mounted in cooling section 400, and condenser coil412 is mounted atop mixing chamber 618.

Advantageously, in the exemplary embodiment of the present invention, aportion of the air that has been cooled in cooling section 400 may alsobe directed through third damper 404 into hot gas reheat coil 406 whenheating section 500 is bypassed by the system (see the arrow labeled “G”in FIG. 5). Reheat coil 406 is typically used to temper the air streambefore it exits unit 100 by way of heated air oulet 504. Hot gas reheatcoil 406 utilizes as portion of the hot gas from the compressordischarge for the purpose of reheating the cooled airflow entering thereheat coil from cooling section 400. Gas is typically discharged fromcompressor 410 at a temperature of about 120° F. (248° C.). Before thisheated gas is directed to condenser 412, the heated gas is diverted tohot gas reheat coil 406. As the hot gas passes through the reheat coil,the refrigerant condenses to a liquid state. The liquid is then directedto the cooling coil expansion valve.

This novel aspect of the present invention permits unit 100 to produce afully dehumidified air stream that is reheated by reheat coil 406 onlyto the extent necessary to prevent any room from becoming undesirablycold under partial load conditions. Thus, when heating section 500 isbypassed, the air that exits the unit and heads toward the rooms withinthe building is either cooled air or tempered air.

When unit 100 is operating in heating mode, cooling coil 402 is inactiveas is hot gas reheat coil 406. Fourth damper 416 allows a portion of theair stream to pass through heating section 500, while the remainder ofthe air stream passes over the inactive cooling coil and out of the unitby way of cooled air outlet 408. Thus, the air that exits the unit andheads toward the rooms within the building is either warm air ortempered air.

The portion of the airflow that is directed into heating section 500passes over heat exchanger 502 which heats the airflow and out of unit100 by way of heated air outlet 504 (see the arrow labeled “F” in FIG.5). The preferred heating source is an indirect gas fired furnace withmodulating burner and cast iron heat exchanger (see description above).Alternate embodiments of air handling unit 100 incorporate differenttypes of heating sources. For example, water, stream, or electric coildevices, or fuel fired furnaces may all be utilized in alternateembodiments of the present invention.

After the cooled, heated, or tempered air has been delivered to theinterior space of the building, the air is returned to air conditioningunit 100 by way of return air inlet 602 (see the arrow labeled “H” inFIG. 5) and is either re-circulated through the unit by blower unit 302or is exhausted from the building through relief air outlet 612 (see thearrow labeled “I” in FIG. 5). Due to the efficiency of the airconditioning unit 100, the amount of relief air that exits the unit istypically very close to the amount of outdoor air delivered to theinternal space of a building with some loss resulting from local exhaustand leakage through the building envelope.

As stated, relief air, which is air returned to the unit from thebuilding, is necessary to equalize the internal and external pressure ofthe conditioned space. The relief air has already been conditioned byair conditioning unit 100, and when the system is in cooling mode, therelief air is considerably lower in temperature than the externalambient temperature. For example, on a typical summer day, the outdoortemperature may be 90° F., while the temperature of the relief air isapproximately 70° F. As described below, this cooler air is utilized bythe present invention to reduce the energy consumption of unit 100.

In an exemplary embodiment of the present invention, condenser coil 412is mounted on the interior of air conditioning unit 100 rather thanbeing physically separated from the other components of the unit.Mounting the condenser coil on the interior of the unit permits thepreconditioned relief air to be directed across the condenser coil byfan 416. By directing the cooled relief air through condenser coil 412,along with a quantity of air drawn from the outside by way of secondaryexternal air intake 618 (see the arrow labeled “J” in FIG. 5), theefficiency of the condenser is enhanced by reclaiming a portion of thecooling energy that is wasted by prior art systems when such cooled airis simply vented as exhaust. Locating the condenser on the interior ofthe unit also prolongs the life of the coils and minimizes the need toclean the coils on a periodic basis. In the exemplary embodiment shownin FIG. 3 a, the conditioned relief air and the air drawn into the unitby way of secondary external air intake 618 are mixed in mixing chamber610. Airflow into mixing chamber 610 is controlled by sixth damper 608and seventh damper 614.

As shown in FIGS. 4 a and 4 b, unit 100 can be fitted with an air-to-airheat exchanger to reclaim energy normally wasted in the exhaust airstream. Energy reclaiming device 700 is typically mounted betweenprimary external air intake 200 and blower section 300 and extends intorelief air section 600. The energy reclaiming device, often referred toa “heat wheel” operates by passing a piece of material, typically analuminum or plastic in a finned configuration, through the primary airintake section and the relief air section in an alternating fashion.Thus, heat present in one air stream is transferred to the other airstream by such a device.

In alternate embodiments, energy reclaiming device 700 is any of avariety of heat exchanger types including a heat wheel, plate fin, or aheat pipe. The heat exchanger can reclaim sensible heat only or bothsensible heat and latent heat depending on the type of energy reclaimingdevice incorporated in to the system.

System Operation

The present invention includes a method for controlling the heating andcooling sections of an air-handling unit to eliminate the possibility ofsimultaneous heating and cooling. This control system utilizes networkcommunications and provides a method for communicating heating andcooling requirements from internal space temperature controllers to acentral device or control module which is typically located on theexterior or interior of the unit. This module provides for an improvedsequence of controls for a dual duct air handler that eliminatessimultaneous heating and cooling and controls the operation of the unitbased on the maximum deviation from the set point of the associatedrooms or spaces.

The system of the present invention may be described as a “hot duct/notso hot duct” or a “cold duct/not so cool duct.” An algorithm is createdwhich is based on polling all the room temperatures and set points anddetermining the maximum call or requirement for heating and cooling.This information is communicated to the air handling unit controller andthe required set points are calculated for each duct. This occurs on acontinuous basis, and over time the set points tend to approach the samevalue. After the set points are calculated, the outdoor air temperatureis used to determine if heating or cooling is required. The unit thenfunctions to satisfy the largest errors with the other spaces byblending air to maintain the interior temperature. A primary advantageof this system is that it provides constant airflow to the interiorspace and therefore constant ventilation is achieved simultaneously.

While the above description contains many specificities, these shouldnot be construed as limitations on the scope of the invention, butrather as exemplification of preferred embodiments. Numerous othervariations of the present invention are possible, and it is not intendedherein to mention all of the possible equivalent forms or ramificationsof this invention. Various changes may be made to the present inventionwithout departing from the scope of the invention.

1. A heat exchanger for use with heated gas, comprising: (a) a firstcylindrical member; adapted at one end to receive heated gas; (b) afirst gas conduit and a second gas conduit positioned in parallel to thefirst cylindrical member; (c) a first collector box in communicationwith the first cylindrical member for dividing the gas flow from thefirst cylindrical member between the first and second gas conduits; (d)a third gas conduit and a fourth gas conduit positioned in parallel tothe first gas conduit and the second gas conduit; (e) a first connectorin communication with the first gas conduit for connecting the first gasconduit with the third gas conduit; (f) a second connector incommunication with the second gas conduit for connecting the second gasconduit with the fourth gas conduit; (g) a second cylindrical memberpositioned in parallel with the third gas conduit and the fourth gasconduit; (h) a second collector box in communication with the third gasconduit and the fourth gas conduit for combining the gas flow from thethird gas conduit and the fourth gas conduit into the second cylindricalmember; and (i) means for creating a flow of the heated gas through theheat exchanger, wherein the means for creating a flow of gas through theheat exchanger comprises a blower positioned within the end of thesecond cylindrical member opposite the second collector box.
 2. The heatexchanger of claim 1, wherein each of the cylindrical members and gasconduits comprise multiple sections.
 3. The heat exchanger of claim 2,wherein the multiple sections further comprise a gasket materialpositioned between the sections for allowing the sections to expand andcontract.
 4. The heat exchanger of claim 1, wherein the heat exchangeris manufactured from cast iron.
 5. The heat exchanger of claim 1,wherein the means for delivering heated gas to the heat exchangercomprises a burner assembly, the burner assembly further comprising: (a)a means for directing uncombusted gas into the burner assembly; (b) adamper for controlling the flow of air into the burner assembly; (c) amixing chamber for mixing the uncombusted gas with air; (d) a sparksource for igniting the gas/air mixture; and (e) a combustion surfacefor enhancing the combustion efficiency of the gas/air mixture.
 6. Anintegrated air conditioning device, comprising: (a) a housing comprisingmultiple sections; (b) a primary air intake for receiving air from theexternal environment; (c) a cooling section, wherein the cooling sectionfurther comprises: (i) a refrigerant; (ii) a plurality of cooling coils;(iii) a first condenser coil in communication with the cooling coils;and (iv) a compressor for moving the refrigerant through the coolingcoils and the condenser coil; and (d) a heating section, wherein theheating section further comprises a heat exchanger, and wherein the heatexchanger further comprises: (i) means for delivering heated gas to theheat exchanger; (ii) a first substantially cylindrical member incommunication at one end with the gas delivery means; (iii) a first gasconduit and a second gas conduit positioned substantially parallel tothe first cylindrical member; (iv) a first collector box incommunication with the first cylindrical member for dividing the gasflow from the first cylindrical member between the first and second gasconduits; (v) a third gas conduit and a fourth gas conduit positionedsubstantially parallel to the first gas conduit and the second gasconduit; (vi) a first connector in communication with the first gasconduit for connecting the first gas conduit to the third gas conduit;(vii) a second connector in communication with the second gas conduitfor connecting the second gas conduit to the fourth gas conduit; (viii)a second substantially cylindrical member positioned substantiallyparallel to the third gas conduit and the fourth gas conduit; (ix) asecond collector box in communication with the third gas conduit and thefourth gas conduit for combining the gas flow from the third gas conduitand the fourth gas conduit into the second cylindrical member; and (x)means for creating a flow of the heated gas through the heat exchanger;(e) a reheat device in communication with the cooling section and theheating section; (f) a return air section, wherein the return airsection further comprises: (i) a return air intake; (ii) means forre-circulating the return air through the cooling and heating sections;and (iii) means for venting return air from the air conditioning device;and (g) a blower section in communication with the primary air intake,cooling, heating, and return air sections and further comprising ablower for creating airflow through the device; and (h) a plurality ofelectronically controlled dampers for controlling airflow through theair conditioning device.
 7. The device of claim 6, further comprising aprogrammable control module for controlling the operation of the airconditioning device.
 8. The device of claim 6, further comprising anenergy reclaiming device positioned within the housing between theprimary air intake and the blower section and extending into the returnair section for redirecting air from the return air section back intothe cooling section and the heating section.
 9. The device of claim 6,further comprising a plurality of air filters in communication with anddownstream from the plurality of electronically controlled dampers. 10.The device of claim 6, wherein the return air section further comprises:(a) a mixing chamber in communication with the return air section; (b) asecondary air intake in communication with the mixing chamber; (c) asecond condenser coil mounted within the mixing chamber; and (d) a fanin communication with the second condenser coil and the externalenvironment for moving air from the mixing chamber across the secondcondenser coil.
 11. The device of claim 10, wherein a first damper islocated within the primary air intake, a second damper is locatedbetween the primary air intake and the blower section, a third damper islocated between the cooling section and the reheat device, a fourthdamper is located between the cooling section and the heating section, afifth damper is located within the return air intake, a sixth damper islocated between the return air section and the mixing chamber, and aseventh damper located within the secondary air intake.
 12. The deviceof claim 6, wherein the means for creating a flow of gas through theheat exchanger further comprises a blower in communication with the endof the second cylindrical member opposite the second collector box. 13.The device of claim 6, wherein each of the cylindrical members and eachof the gas conduits further comprise: (i) a plurality of individualsections detachably joined to one another; and (ii) gasket materialpositioned between the individual sections.
 14. The device of claim 6,wherein the gas conduits are manufactured from cast iron.
 15. The deviceof claim 6, wherein the means for delivering heated gas to the heatexchanger comprises a burner assembly, and wherein the burner assemblyfurther comprises: (a) means for directing uncombusted gas into theburner assembly; (b) a damper for controlling the flow of air into theburner assembly; (c) a mixing chamber for mixing the uncombusted gaswith air; (d) a spark source for igniting the gas and air mixture; and(e) a combustion surface for enhancing the combustion efficiency of thegas and air mixture.